Well now you have met one though to be honest I really have not given that particualr aspect of libertarian thought a whole lot of time untill now.
That's why I phrased it the way I did. I was not making a True Scotsman claim, I stated the fact I've never met a libertarian who didn't support loser pays. Or as you say, until now. Loser pays is one solution, so I think it's clearly a True Scotsman fallacy to say a libertarian has to support that specific solution.
However, the right to be made whole when you are wronged is a clear libertarian value. Whether or not loser pays is the specific solution, I don't see how a libertarian would not support the ability to in some way sue back for a frivolous or malicious lawsuit. I see three hypothetical options:
1) Loser pays - automatic
2) Follow on trial after verdict to determine if and how much loser will pay. Sort of like after a murder trial there can be a follow on trial attached to determine whether or not to have the death penalty
3) Loser can file a separate lawsuit.
I would have a hard time processing that a libertarian would reject the idea of losers pursuing compensation with the burden shifting to them to prove the lawsuit was not filed with honest intent
I, personally, think that the entire system needs to be reworked and the end result might not even matter as far as looser paying. The idea that I have to expend massive amounts of money to defend my rights or persue those that have broken them just smacks of corruption to me. I would definately support a loser pays system in blatant cases but I am not so sure if the case is legitamately muddy.
So from this, I would guess you support option 2?